Photographic material



June 4, 1940.

UE/VS/ Ty E. B. MIDDLETON Er Ax. 2,202,992

PHOTOGRAPHIC MATERIAL -Filed Nov. 13, 1957 f/vs/T/ l//Ty RHA/GE EMULS/0N W/THOz/T WE Emma/@762577,

660759@ (Z. en/Sofa, @y 15 @y -Patented June 4, 1940 NUNITE-D STATES PATENT oFFlcE PHOTOGRAPHIC MATERIAL Edmund B. Middleton, Metuchen, and George A. Dawson, Raritan Township, Middlesex County, N. J., asaignors to Du Pont Film Manufactuing Corporation, New York, N. Y., a corpora- V tion ol Delaware Application November 13, 1937, serial No. 114,472

12 Claims.

This inventiomrelates to photographic emulsions containing methine cyanine dyes and has foran object the provision o1 new and useful photographic emulsions containing methine cyanine dyes having a bisazole nucleus, more par- '5 ticularly cyanine dyes containing the nucleus aration of gelatino silver halide photographic emulsions having as sensitizers cyanine dyes containing a bisthiazole nucleus, preferably a benzo-bisthiazole nucleus of the type in which the hydrogens of the benzene ring may be further substituted. A still further object is the preparation of photographic emulsions containing dyes of the type described in which one of the nitrogen atoms of the bisazole nucleusv 35 is trivalent and the other pentavalent. Other objects will appear hereinafter.

These objects are accomplished by the incorporation into photographic emulsions, for example, gelatino silver halide emulsions such as emulsions, of methine cyanine dyes containing a .bisazole nucleus.- An azole has a poly-heteroatomic ve-membered ring which contains nitrogen and oxygen, nitrogen and sulfur, nitrogen separated from other nitrogen or other hetero atoms in the ring by the carbon atoms, two of zobisazole refers'to a compound in which two vpairs ofV ortho-carbon atomsxo! a benzene ring ilver chloride emulsions and silver bromidek and selenium or two nitrogen atoms, the remaining atoms being carbon atoms. The nitrogen is are shared by two azole rings. of this nomenclature are benzobisoxazole, Chemical Abstracts, vol. 16, page 1428; benzobisselenazole, Chemical Abstracts, vol. 16, page 1428; and benzobisthiazole, Chemical Abstracts, vol. 16,

page 2509. If the common nucleus between the azole rings is aJ2 naphthalene nucleus, the entire nucleus is a naphthbisazole nucleus, as, for example, a naphthbisoxazole, a naphthbisselenazole or a naphthbisthiazole. f

Generically, the dyes of this invention may be called bisazolel` methine cyanine alkyl salts. They are characterized by having a carbon atom alpha to a quaternary nitrogen atom of a bisazole nucleus connected through a methenyl. or methine carbon atoin or chain to the alpha or Specific examples gamma. carbon atom of another heterocyclic nitrogen nucleus. As is the case with all methine cyanine dyes they have alkyl groups on the pentavalent nitrogen atoms of the heterocyclic nuclei. The preferred dyes are arylbisazole methine cyanine alkyl salts.

These dyes may be prepared by the following steps: (l) converting a diamine to a di-mercapto di-azole of the oxygen group of elements; (2) g llwlating to produce the dithioethers; (3) converting the dithioether to a quaternary salt; and (4) reacting the said quaternary salt with a quaternary salt of a heterocyclic base containing an alkyl group in the alpha or gamma positions. In this manner 'a whole new series of dyes can be produced. Furthermore, if the active alkyl group on the heterocyclic base is methyl, the methine group will be unsubstituted, but if the active group is ethyl, propyl, etc., the methine group will be substituted by methyl, ethyl, etc.

v'I'he invention is specifically illustrated withI reference to methine dyes containinga bisthiazole nucleus. 'I'he mercapto derivatives of bisthiazoles can be obtained by heating amines with carbon disuliide and' sulfur under pressure. For example, the bisthiazole having the structure is readily prepared by heating one mole of p-phenylene diamine with 2.2 moles of carbon` .disulfide and 2 moleso sulfur to 240i C. for six diamine, naphthylene diamines, methyl diaminobenzene, and the like.

'I'he di-mercapto derivatives are then alkylated by known methods, so that the di-thioethers are may be prepared by treating the correspondingl dimercapto compound with dimethyl sulfate and alkali in the usual way. The di-thioethers are then converted to the quaternary salts by heating with an ester of organic or inorganic acid (e. g., diethyl sulfate, ethyl p-toluene sulfonate, as described in the examples). The quaternary salts -are then converted to cyanines by treating them with quaternary salts of heterocyclic bases containing alkyl groups in the alpha or gamma positions, in the 'presence of an acidbinding agent, as described in the examples.

In carrying out the invention, certain observations have been made as follows. i' In the rst place, it appears that generally only one ring of a bisthiazole nucleus will form a quaternary salt, the other remaining tertiary. Furthermore, generally only one of the thioether groups will condense. Ethyl iodide does not add to the bisthiazole vbase to form a salt in the case of the. bisthiazole from p-phenylene diamine, but quaternary salts are obtained by heating the base with ethyl p-toluene sulfonate or with diethyl sulfate. Depending upon the temperature at which the quaternary salt is formed; the cyanine dyes obtained by condensing the dithioether bisthiazoles with Quaternary salts of 2-alkyl thiazoles, 2-alkyl selenazoles, and 2-alkyl oxazoles will vary in shade from yellow to orange, caused apparently by the formation of dye containing both rings of the thiazole condensed.

The preferred dyes may be given the general formula in which Y and Z represent members oi' the oxygen group of elements (e. g., -O-, -S', -Se-) preferably sulfur, X represents the negative radical of an acid (e. g., -I-, `-Cl, -Br, sulfate, chlorate, p toluene sulfonate, etc.), R and R1 represent aromatic radicals preferably of the benzene or naphthalene series, A represents -H or. alkyl, B represen@ a member ofthe oxygen group of elements (-0,`-S'-, -Se-) dialkyl methylene Jr vinylene (-CH=CH), and the numerals indicate condensation positions when B is vinylene.

The sensitizing effect of some of these dyes on gelatine silver chloride emulsions is illustrated' in the accompanying drawing.

The invention will be further illustrated but 'is not limited by the following (examples, in

which the quantities are stated in parts by weight.

EXAMPLE I Y Twenty-five (25) parts of the dimercapto ditaining 20 parts (excess) of caustic. The solution was warmed to 40 C. and treated dropwise with 30 parts of dimethyl sulfate. The `flask was shaken continuously and cooled to keep the temperature between 40 and 50 C. A white solid precipitated from the green solution, and after several crystallizations from alcohol, it was obtained pure enough for analysis. This was the dithio methyl ether of benzobisthiazole from p-phenylenediamine, melting at 153 C. and having the formula f s CH.s-=N A sample oi' the base prepared as above described was heated over night in a sealed tube with excess ethyl iodide (over two equimolecular proportions) at ten pounds steam pressure. The product was crystallized several times from alcohol and analyzed. It had a melting point of 155,1 C. The mixed melting point with the lbase was 12S-136 C. It did notshowa qualitative test for iodine. 'I'he fact that a mixed melting point ofthe product from this reaction and the parent substance is noticeably depressed is proof that the two -are not identical compounds? The quantitative determination of the sulfur content is in close agreement with the calculated requirements of a compound similar to the parent substance except that one of the methyl groups has been exchanged for an ethyl group.

A second reaction in which the time of heating was prolonged, and the temperature oi the eaction increased was run. This time the prodf ct was separated into several fractions according to their solubilities in alcohol. They had melting points of l97200 C. and 240 C. respectively. Neither of these fractions yielded a qualitative test for iodine. It thus appears that this base does not form a salt with ethyl iodide, but the quaternary salts were readily obtained by heating the base with ethyl p-toluene sulfonate 0r with diethyl sulfate.

Preparation of the cyam'ne dye having the were heated 3 hours at 160 C. with 1.4 parts (excess of 2 moles) of ethyl p-toluene sulfonate. The melt when cool was dissolved in about 24 parts. of absolute alcohol and 4.3 parts (2 moles) of 2-methyl benzothiazole ethiodide were added. The mixture was heated to reux and an excess of fused sodium acetate added over that required to bind the free acid. An orange colored dye precipitated. It was reuxed 15 minutes, recrystallized twice from alcohol, and obtained as brown-orange crystals.

B. About 0.5 part of dimethyl thio ether benzobisthiazole from p-phenylenediamine, prepared maximum was 4700 A. and it extended the sensi' 2,202,992v as described above, was heated 2 hours at 130- 150 C. with .54 part (2 moles) of'diethyl sulfate. On cooling, the melt was dissolved in 16 parts of absolute alcohol, heated to reflux with 1.1 parts of Z-methyl benzothiazole ethlodide and .3 part of fused sodium acetate then added. A yellow dye precipitated. The mixture was reiluxed for 15 minutes, cooled, and thedye totally precipitated with water, filtered and recrystallized twice from alcohol as yellow-orange crystals. In a silver-chloride emulsion it produced sensitivity maxima at 4750 A. and 5050 .0 and extended the sensitivity to 5500 A.

C. One part of 2,2' dimethyl thio benzobisthiazole from p-phenylenediamine (melting point 152153 C.) and 1.1' parts of diethyl sulfate were heated 2 hours at110-120 C. On cooling,

the melt was dissolved in 20 parts ethyl alcohol, treated with 2.15 parts of 2-methyl benzothiazole ethiodide and heated to reflux. Then .5 part of fused sodium acetate was added, and reuxing continued for 15 minutes. The dye reaction proceeded slowly and crystals were not obtained until the solution was cooled; after precipitating with water and recrystallizing twice from alcohol, light yellow crystals were obtained. In a silver chloride-emulsion of the' dye, the sensitivity tivity to 5300 D. Two parts (1 mole) of dimethyl thio benzobisthiazole from p-phenylenediamine prepared as above were heated several days with 1.2 parts of diethyl sulfate dissolved in benzene, on a steam bath. Yellow crystals were obtained. The benzene Was evaporated under vacuum at 100 C. and the crystals dissolved in 20 parts of absolute alcohol. 2.2 parts of 2-methyl benzothiazole ethiodide were added and the solution heated to reflux. Then .2 part of fused sodium acetate was added and the mixture refluxed 15 minutes. The reaction proceeded slowly, and on cooling a yellow dye precipitated. When recrystallized twice from alcohol, light yellow crystals were obtained.

From the experiments described, it is evident that the chief product formed in the dye reaction is the product containing but one ring of the bisthiazole condensed with one molecule of Z-methyl benzothiazole ethiodide. When the quaternary salt of the bisthiazole is formed at a low temperature, the dye obtained is in its purest form, as evidenced tby its light yellow color and the single maximum it produces in a silver chloride emulsion, but when the quaternary salt is formed at a high temperature, a trace of the dye is formed by the condensation of both thiazole rings of the bisthiazole, but not in sufcient measure to change a quantitative sulfur analysis l by much. The color of the dye is changed from yellow to orange-yellow, however, Iand a second `sensitizing maximum of a longer wave length is produced by it in a silver chloride emulsion.

EXAMPLE II Preparation of dye having thejormula CxHI oH=s-i=N 2.9 parts of the ethsulfate from dithio methyl ether of benzobisthiazole from p-phenylenediamine were dissolved in 36 parts of ethyl alcohol and treated with 3 parts of lepidine ethiodide. 'Ihe mixture was heated to refluxing and 1.1 parts of fused sodium acetate added. A -red colored solution was formed and CHaSH escaped. On cooling, dark red crystals formed and were recrystallized twice from alcohol.

When added in suitable amount to a silver" bromide emulsion this dye showed sensitizing maximum at 5450 A. and extendedo the sensitivity of the emulsion to 6200 A.

ExmLl 111 i I Preparation of due having following formula 2.4 parts of the'ethsuiface of dithio methy1 ether ofbenzobisthiazole from p-phenylenedlamine were dissolved in 36 parts of absolute alco' hol and treated with 3 parts of beta-naphthoquinaldine ethiodide, heated to reuxv and 1.1 parts of fused sodium acetate added. A red colored solution was produced, and on cooling red crystals were formed after recrystallizing twice from alcohol.'

The dye is a weak sensitizer for silver bromide emulsion with a maximum at 5450 A. It extends the sensitivity of the emulsion to 5700 A.

Four n(4) parts of the ethylsulfate of the dithio dimethyl ether of benzobisthiazole from p-phenylene diamine were dissolved in 36 parts f absolute alcohol, 5 parts of 2-methyl benzoselenazole ethiodide added, and the mixture heated to reux. 2.2 parts of fused sodium acetate were added and refiuxing continued for 15 minutes. 'Ihe dye was precipitated with water and recrystallized twice from alcohol as yellow crystals.

It is a powerful blue sensitizer for silver chloride emulsions, with a high maximum at 4800 A. nd extending the sensitivity to 5700 EXAMPLE V Preparation. of dye having the formula EXAMPLE VI A.-Preparation of 4the dimethyl ether of tolyl` l bisthiazole CHa C-SCH:

Fifty (50) part'sof the dimercaptide of y tolyl bisthiazole were heated to reflux in an alcoholic potash solutioncontaining nineteen parts of potassium hydroxide and 240 parts of absolute ethyl alcohol. The heat\ source was then removed and the solution treated dropwisewith forty-seven parts of dimethyl sulfate at rate just sufficient to keep the mixture boiling. When this had been added, the refluxing was continued for an hour, and then the mixture was cooled. 'I'he dimethyl ether started precipitating towards the end of the methylating procedure', and was ltered, washed with twoY percent sodium car bonate solution and then with water and alcohol. After recrystallizing from alcohol the product was obtained as a light yellow solid melting at 136, rather insoluble in organic solventsl1 and not soluble in water or dilute alkali. It can be vacuum distilled, yielding snow white crystals melting sharply at 136, but the crystallization alone gives a product of suiiicient purity for further work. v

B.-Preparation of. the cyanine dye having the Two parts of the dimethy1 tmoetner of tolyl bisthiazolewere heated with 2l parts of ethyl p-toluene sulfonate for 4 hours at 160-180 C.' "I'hen the mixture was cooled and dissolved in 24 parts absolute alcohol, 4.1 parts of 2-methyl benzothiazole ethiodide added and the mixture warmed until solution was complete. Then 1.1 parts of fused sodium acetate were added to the mixture. A yellow precipitate of the dye immediately formed and the reaction was completed by refluxing the mixture ve minutes. The odor of methyl thio alcohol was also apparent. The dye was filtered, washed with water and recrysaaoaooa tallized from alcohol. When incorporated in a.

silver halide emulsion, the dye had a sensitizing maximum at 4700A.i50 A.

EXAMPLE VII Preparation of the cyamne dye having the formula la.. t,...

Two parts of the dithio methyl ether of tolyl bisthiazole (prepared as in Example VI A) and 3.2

parts of ethyl p-toluene sulfonate were heated together at C for four hours. The melt was cooled and dissolved in 40 parts of alcohol. 4.73 parts of 2-methyl benzoselenazole ethiodide were then added, and the solution heated to reux, with the addition of 1.1 parts of fused sodium acetate, and the reuxlng continued for 10 minutes. The yellow precipitate that-formed was filtered, washed well with warm water followed by alcohol, and recrystallized from alcohol as yellow crystals. The sensitizing maximum was at 4750 A.i50 A.

EXAMPLE VIII Preparation of the cyam'ne dye having the formula C--SCHI 'rwo parts of the dithio methy1 ether of tolyl bisthiazole (prepared as in Example VI A) were heated with 3.2 parts of ethyl p-toluene sulfonate at 150-180 C. for four hours. The melt was cooled and 24 parts of absolute alcohol added.

Then 4 parts of quinaldine ethiodide were added and the mixture heated to reilux, after which 1.1

parts of fused sodium acetate were added and reuxing continued 15 minutes. A brick red precipitate formed, was iiltered, washed with water and recrystallized from alcohol as scarlet crystals. 'I'he sensitizing maximum was at EXAMPLE IX Preparation of the cyam'ne dye having the formula Three parts of the di-thio methyl ether of benzobis'thiazole from m-phenylenediamine was heated -2 hours at 13D-140 C. with 3.5 grams of diethyl'sulfate. 'I'he melt was cooled and dissolved in 40 parts of alcohol. To this solution 9.2 parts of 2:5 dimethyl benzoselenazole ethiodide were added and the mixture heated to reiiux; .then 2.05 parts of fused sodium acetate were added and reuxing continued for 20 minutes thereafter. The yellow-orange dye that precipitated was filtered and recrystallized from alcohol.

When .015 gram of this dye dissolved in 30 cc. of alcohol is added to one liter of silver chloride n emulsion, an extra sensitivity is added, extending to 5300 A. and with a maximum at 4700 A.

Exmin jX Preparation of the cyam'ne dye having the formu'la CaHl CHI I The ethsulfate of 2,2 dithio methyl ether of tolyl bisthiazole, prepared by heating 2 p'arts of the 2,2' dithio methyl ether of tolyl bisthiazole from tolyl m-diamine 2 hoursA at 13o-140 C.,

with 2 parts of dimethyl sulfate, was dissolved in 40 parts of alcohol. parts of lepidine thiodide, heated to refiux, and

1.1 parts of fused sodium acetate added. The

mixture was refluxed 15 minutes, cooled and ltered from the red colored crystals which were recrystallized from alcohol. If .015 gram of'this dye is 4dissolved in 30 cc. of alcohol and added to one liter of a photographic emulsion, an extra sensitivity is conferred, extending to 5800A. and with a maximum at 5500 A.

EXAMPLE XI Preparatiornof the cyanne Vdye having the formula y alcohol.

0.9 part f b-naphtha qmnaldxne ethiodide was dissolved in 12 parts of alcohol and treated with .4 part of the ethsulfate from the dithio methyl ether of tolyl bisthiazole. The mixture was heated to redux and then .19 part of fused sodium acer tate added. Reuxing was continued for minutes and then the mixture was cooled, ltered from red crystals which were recrystallized in If .015 gram df this dye in 3o ce. of alcohol 1s added to one liter of photographic emulsion, an'.

extra sensitivity is conferred that extends to 5800 A. with a maximum at 5600 A.

It was then treated with 4 EXAMPLE n Preparation of the cyanne d/ye having the formula CHa 03H; CIHI l /Cimsm parts of alcohol, and treated with 2.3 parts of the ethsulfate of 2 methyl b-naphthothiazole also ,dissolved in parts of alcohol. The solution was heated to reux and then treated with 1.1 parts of fused sodium acetate. It was reiiuxed l5 minutes, and the solution poured into a Warm, saturated, aqueous solution of potassium iodide, cooled and filtered and the orange-brown precipitate recrystallized from alcohol.

vWhen .015 gram of this dye is dissolved in 30 cc. of alcohol and added to 1 liter of emulsion,

an extra sensitivity is conferred that extends to 5700 A and has a maximum at 4800 A,

EXAMPLE IEZIE Preparation of the cyamne dye having the formula GHz To prepare the dye whose structure is drawn above, follow the directions and quantities in Example m, with the exception that 3.9 parts of 2 methyl benzoxazole ethiodide are substituted for the 2 methyl b-naphthothiazole ethsulfate. After recrystallizing from alcohol, dark brown crystals are obtained.

When .015 gram of this dye is dissolved in 30 cc.y of alcohol and added to one liter of emulsion, an-extra sensitivity is conferred that extends to 5400 A and has a minor peak at 4700 A and a major peak at 4300 A. v

EXAMPLE XIV Preparation of the cyanine dye having the formula s s\ s oms-o o-cn=o i \N N NY Two parts of 2,2' dithio methyl ether of benzo- Avbisthiazole prepared from m-phenylenediamine were heated 2 hours at 13o-140 C. -with 2 parts of diethyl sulfate. To the cooled melt'were added 3.47 parts of 2-methyl benzothiazole ethiodide dissolved in 40 partsof alcohol. The mixture was heated until solution was complete, and then brought to a boil and 1.15 parts of fused sodium acetate. added. 'A yellow color developed in the solution and a solid precipitated. Reuxing was continued'for 15 minutes, and the mixture then cooled and filtered. After three crystallizations from alcohol, yellow-brown crystals were obtained.

When, o gram of this cLve .is dissolved in 3o cc. of alcohol and added to one liter of emulsion,

an extra sensitivity is conferred that extends to 5400 lik, with maxima at 5300,4700 and 4300 A.

y ExAMPLl.' XV Preparation of the cyanine dye having the formula ls s s oms-c/ \oc=c/ t N N E \N- om l I CaHs The above dye was obtained by the procedure of Example XIV with the exception that 4.6 parts of 2 ethyl 5 methyl benzothiazole ethiodide was substituted for 2 methyl benzothlazole ethiodide. When recrystallized twice from alcohol, light yellow crystals were obtained.

When .015 gram of this dye-is dissolved in 30 cc. of alcohol and added to one liter of emulsion,

an extra sensitivity is conferred that extends to,

5500 A and has maxima at 5300, 4700 and 4300 A.

ExAuPLr: XVI

Preparation of the culmine dye having the formula an extra sensitivity is conferred that extends to 5600 A with amaximum at 5400 A.

EXAMPLE XVII Preparation of the cyanine dye having the formula Urli:

The above dye was prepared according to instructions given in Example XIV, using 4 parts of 2 methyl benzoxazole ethiodide in placel of 2 methyl benzothiazole ethiodide. The dye after crystallizing twice -was obtained as olive green crystals.

lWhen .015 gram of this dye was dissolved in 24 parts -oic alcohol and added to one liter of emulsion an extra sensitivity was conferred that exytendedto 5200 Awith maxima at 4800 A and ExAuPLn XVIII Preparation of the cuaninedye having the formula The above dye was prepared as in Example XIV, using 4.2 parts of lepidine ethiodide in place oi.' 2 methyl benzothlazole ethiodide. The product when crystallized twice from alcohol was obtained as dark red crsytals.

When .015 gram of this dye was dissolved in-24 parts of alcohol and added to one liter of emul-v sion, an extra sensitivity was conferred that extended to 5800 A. and had a maximum at 5400 A.

Variations may be made in preparing the dyes without departing from the invention. Thus,

instead of using lepidine ethiodide, we may use quaternary salts of 6-methyl lepidine, -ethoxy lepidine, 7:8-benzolepidine; or other lepidine derivatives in the examples. Instead of 2- methyl quinoline ethiodide, we may use quaternary salts of 2-methyl quinoline derivatives, for

example, containing alkyl substituents (methyl,l

ethyl, etc.), halogen (-I, -Cl, -Br, F), or alkoxy' (methoxy,) ethoxy, etc.) Y in the aromatic ring. Instead of quaternary salts of unsubstituted 2-alkyl oxazoles, selenazoles and thiazoles, we may use the substituted derivatives, e. g., 2:5-

dimethyl benzo thiazol'e ethiodide, 2:5-dimethylc benzo selenazole ethiodide, 2-ethyl-5-methylbenzo thiazole ethiodide, 2ethyl5methylbenzo selenazole ethiodlde, and other substituted derivatives containing allql (e. g., methyl, ethyl, etc.) alkoxy (methoxy, ethoxy, etc.) halogen I, -Br, CD or dialkylamino (dimethylamino, diethylamino, etc.) in the aromatic ring'. Other intermediates having condensed rings, ve. g., 2-

methyl alpha naphthoselenazole ethiodide, may used. If desired, the 2alkyl quaternary salt may be a simple thiazolo, selenazolo, or oxazolo base, e. g., a quaternary salt of 2:4-dimethyl, thiazole, 2:4-dimethyl oxazole, 2:4-dimethyl selenazole, 2-methyl-4-phenyl thiazole, 2-methyl-4r5-diphenyl thiazole, and the like. The aromatic portion of the bisazole nucleus may also contain other substituents, e. g., other alkyl substituents, or alkoxy radicals quaternary salt may also be an indolenine, e. g., 2 3 3-trimethyl-indolenine ethiodide.

' W'hile we preferably form the new cyanines from the thioether derivatives, we may employ the corresponding'intermediates except that the thioether groups are replaced by alkyl groups', e. g., 2:6-dimethyl benzohisthiazole` 4 This is converted to the quaternary salt in the usual manner and one mole `thereof reacted with 1 to 2 moles oi' alpha iodo quinoline ethiodide, or other 2-halogeno quinolino quaternary salt, in the presence of an acid binding agent and solvent,l e. g., alcohol and caustic alkali, or an organic (methoxy, ethoxy, etc.) ,in place of hydrogen. The 2-alkyl 'base such as triethylamine, tri-n-propylamine, etc., to produce apseudocyanine. With 4halo geno` quinolines, in the presence of a` condensing agent, thev isocyaninesare formed.

If a carbocyanine is desired, a dialkyl dithiazole quaternary salt, or other dialkyl diazole quaternary salt, is reacted with an alkyl ortho ester such as ethyl ortho formate, ethyl ortho acetate, etc. This produces a symmetrical carbocyanine containing two dithiazole nuclei. To produce lateral carbon atom substitution dlethyl dithiazole quaternary salts may be employed. To produce an unsymmetricalcarbocyanine, the

. dialkylthiazole may be reacted with a diarylamidine, e. g., diphenyl formamidine, diphenyl acetamidine, etc., and the resultant intermediate reacted with a quaternary salt of a y 2-alkyl oxazole, thiazole, or selenazole such as those described above. By using the 2-ethyl and higher derivatives, substitution on the lateral carbons of the trimethine chain is obtained. This reaction is usually effected in the presence of acetic anhydride and sodium acetate.

symmetrical and unsymmetrical methine dyes having a pentamethenyl chain may be prepared by reacting a dialkyl bisthiazole quaternary salt with a beta anilino acrolein anil in acetic anhydride and then condensing the resultant intermediate compound with the same or another quaternary salt, e. g., 2-methyl benzothiazole ethiodide, 2,-methyl benzoselenazole ethiodide, etc.. in the presence of acetic anhydride and sodium acetate. f

In the examples, we usually prepare the bisthiazole quaternary salts by reacting 1 mole of a dimercapto bisthiazole with 2 or more moles of an ester of an organic or inorganic acid. However, wemay effect the reaction with 1 mole of ester per mole of dimercapto bisthiazole. In other words, we may use the theoretical proportions required .to ,form the desired Quaternary salt or we may use an excess of the ester. If an excess of the dimercapto dithiazole is employed, the reaction will not be complete, although some reaction will occur. In forming the dyes from the quaternary salts of the bisthiazole derivatives and the other heterocyclc compounds having reactive alkyl groups, we sometimes employ 2 moles of said heterocyclc compounds per mole of `bisthiazole Quaternary salt. This reaction, however, may be effected with 1 mole of one of said heterocyclc compounds per mole of bisthiazole quaternary salt. Naturally, where an excess is used, it does no harm and the unre- .acted compounds can readily be removed from the reaction mixture. For instance, 'in Example II, we could effect the reaction with 2.2 parts of the ethosulfate, 1.5 parts of lepidine ethiodide and .5 part of sodium acetate. Similarly, we can employ smaller proportions ofv heterocyclc quaternary s'alt and acid binding agent in the examples following Example II. At the same time we can decrease the proportions of ester used in4 forming the bisthiazole quaternary salt. For instance, in Example IX, we can effect the reaction with 2.8 parts of dimethyl dithiobenzoblsthiazole, 1.5 parts of diethyl sulfate, 3.7 parts of dimethyl benzoselenazole ethiodide and 1 part of sodium acetate.

The dyes may be used in photographic emulsions according to any of the usual methods employed in the photographic art. lUsually a stock solution of the dyeis rst prepared by dissolving it in a suitable solvent, for example, an alcohol such as methyl or ethyl alcohol. Then,

into onel liter of photographic gelatino silver halide emulsion is incorporated a small amount of dye, say.' .0l to .04 gram. The quantity of dye may vary depending upon the particular dye, the type of .photographic emulsion and the results desired. The sensitized emulsion may then be coated on plates or films. -As` will 'be observed from the examples, the dyes may be used in gelatino silver chloride emulsions and gelatino silver bromide emulsions. Certain of the dyes are particularly powerful sensitizers for silver chloride gelatine emulsions.

Since cyanine dyes containing a bisazole nucleus have not heretofore been described, insofar as we are aware, we have described them by their structural characteristics. That is to say, they may be described broadly as methine cyanine dyes having two N-heterocyclic nuclei, at least one of which is a bisazole nucleus, joined by a methine carbon atom or a methenyl chain between a carbon atom alpha to a quaternary nitrogen atom of the bisazole nucleus and a carbon atom in one of the positions alpha and gamma to the nitrogen atom of the other N- heterocyclic nucleus. Inasmuch as a cyanine dye' always contains two N-heterocyclic nuclei connected by a methine-carbon atom or methenyl chain, this description should be clearly adequate for any one skilled in the art to understand it. We may also refer to our new dyes more specilically as thiobenzobisthiazole monomethine cyanine dyes (for instance, the dye of Example I), selenobenzobisthiazole monomethine cyanine dyes (for instance, the dye of Example IV), exabenzobisthiazole monomethine cyanine dyes (for instance, the dye of Example XIII), benzobisthia'zole methine isocyanine dyes (for instance, the dye of Example IIL/and benzobisthiazole dyes (for instance, the dye of Example III). More broadly, these same types of dyes may be described as thioarylbisazole monomethine cyanine dyes, selenoarylbisazole monomethine cyanine dyes, oxarylbisazole monomethine cyanine dyes, arylbisanole pseudocyanine dyes and arylbisazole isocyanine dyes.

In our copending application Serial No.` 129,958, filed March 9, 1937, we have claimed the blsazole methine cyanine dyes as new compounds. In application-Serial No. 142,283, filed May 12, 1937, carbocyanine dyes containing a bisazole nucleus are described and claimed.

As many apparently widely different embodiments of this invention may be made without departing from Athe spirit and scope thereof, it is to be understood that we do not limit ourselves to thespecic embodiments thereof except as described in the following claims.

We claim:

1. A gelatino silver halide photographic emulsion containing as a sensitizer a bisazole methine cyanine dye.

2. A gelatino silver halide photographic emulsion containing as a sensitizer an aryl bisazole methine cyanine dye.

3. A silver halide photographic emulsion conmiI taining as a sensitizer a bisazole X-monomethine cyanine salt in which X is a member selected from the group consisting of oxazole, selenazole, thiazole and quinoline.

4. A silver halide photographic emulsion con- 5. A silver halide photographic emulsion containing a benzobisazole-benzoselenazole-mono- 'methine cyanin'e salt.

in which Y and Z represent members of the oxygen group of elements, X represents the negative radical of an acid, R and R1 represent aromatic radicals selected from the group consisting of radicals of the benzene and naphthalene series, A represents a radical selected from the group consisting of -H and alkyl, B represents a member of the oxygen group of elements, dialkyl methylene and vinylene, and the numerals indicate condensation positions when B isA vinylene.

10. A photographic material comprising a gelatino silver halide emulsion containing a sensitizing dye having the following formula in 'which X represents the 'negative radical of an acid, R and R1 represent aromatic radicals selected from the group consisting of radicals of the benzene and naphthalene series, A represents a radical selected from the group consisting o1' -H and alkyl, B' represents a member of the oxygen group of elements, dialkyl methylene and vinylene, and the numeralsindicate condensation positions when B is vinylene.

11. A photographic'material comprising a ge-v latino silver halide emulsion containing a sensitizing dye having the following formula in which X represents the negative radical of an acid, R and Ri represent' radicals of the benzene series, and B represents a member of the oxygen group of elements. l

12. A photographic material comprising a gelatinosilver halide emulsion containing a sensitizing dye having the following formula S S A B in which X represents the negative radical of an acid, R and R1 represent radicals of the benzene series, A represents alkyl, 'and B represents a member of the oxygen group of elements.

EDMUND B. MIDDLETON. GEORGE A. DAWSON.

` l CERTIFICATE CF CORRECTION. Patent No. 2,202,992. June h., 19M),

EDMUND B. MIDDLETON, ET AAL;`

It is hereby certified that error appears' inthe printed specification ofthe bove numbered patent requiring correctinae follows': .Page 5', first column, line 52, for "dimethyl" read diethyl; line 5b., for "thiodide" read -ethiodide; and that the said .Letter's Patent should be read with this `Correction therein thatthe same may conform to the record of the c'ase 4 in the lfatent Office.

signed and sen-,11ml this 27th day of August, A. D. 191m.

. Henry Van Arsdale Y (Seal) Acting Commissioner of JEtents. 

